SU‐FF‐T‐607: Immobilization, Treatment Planning and Treatment Delivery for Breast Irradiation with Protons

Purpose: To describe a technique for partial breast irradiation with proton beam radiotherapy. Method and Materials: A breast patient post lumpectomy is fitted with a special brassiere to reproducibly support the ipsilateral breast while compressing the contralateral breast. The patient then lies prone in a PVC half cylindrical pipe, supported from shoulder up and below the abdomen by foam bead cushions. The air from the cushions is evacuated resulting in rigid immobilization. The breast area is then immobilized with a urethane based foaming agent producing custom immobilization of the ipsilateral breast. Next, the patient undergoes a treatment planning CT scan of the thorax. The physician contours the tumor bed to include surgical clips and then contours organs at risk. A 3D conformal treatment plan is then developed. For every treatment, the patient is fitted with the treatment brassiere, and positioned prone in the custom immobilization device. Orthogonal and treatment angle diagnostic x‐ray images are taken prior to treatment and are compared with the treatment planning DRRs to reproduce the treatment position according to the plan. The titanium clips are used in the alignment process. At least two fields are treated each day delivering a daily dose of 4.0 cobalt Gray equivalent, and a total dose of 40 cobalt Gray equivalent in 10 fractions. Results: 60 patients have been treated so far. Immobilization procedure is highly reproducible. A comparison with a photon plan demonstrates the clear advantage of a proton treatment to spare the organs at risk, including a significant decrease in skin dose. Conclusion: The immobilization procedure provides an accurate and reproducible breast positioning, and minimizes respiratory motion. The procedure has been well tolerated by most patients treated so far. Protons provide significant normal tissue sparing as compared to photon treatments and the clinical results look encouraging. © 2009, American Association of Physicists in Medicine. All rights reserved.